On what surface was the oldest book known to anthropologists composed?

The oldest known books, specifically the texts that are recognized by anthropologists, were composed on clay tablets. The use of clay tablets dates back to ancient Mesopotamia, around 3500 BCE. These tablets were inscribed with cuneiform script, which is one of the earliest systems of writing.

Clay tablets were advantageous because they could be baked to harden, making them durable and capable of preserving texts over time. They provided an effective medium for recording everything from administrative records to literature, allowing for the storage and transmission of knowledge in a way that previous materials could not.

While other surfaces such as papyrus and animal skins were widely used in different cultures later on, the clay tablets hold the distinction of being among the earliest forms used for documenting information. Stone tablets, while also ancient, were less common for the lengthy texts we consider as books today due to their heaviness and the difficulty of inscribing them.